1. Field of the Invention
This invention relates to the coating of any fluent, directly onto any three-dimensional web surface resulting in a high coat weight deposition of said fluent coating to mainly reside on the upper/outer most surface of said three-dimensional object, including the apparatus required to meter and transfer the fluent coating.
The method and system of this invention provide for applying and coating a cushion with adhesive for mounting the cushion between a plate cylinder surface and a flexographic plate surface as described in U.S. Pat. No. 6,247,403. The adhesive is applied to the tips of the protrusions that make up the structure of the cushion.
2. Description of Prior Art
Fluent coating applies broadly to many processes, in many industries, including, many categories of prior art used for coating a continuous web. Most are used for the coating of a two-dimensional surface including most commonly, Direct Gravure, Reverse Gravure, Reverse Roll, Slot Die/Curtain Coating, Spraying, Brushing, each of which may contain multiple iterations including the ability to restrict the area in which the fluent coating is being applied, including masking, pattern coating, and other various techniques.
1) Brushing is a coating process whereby a brush is dipped into a fluent coating and the saturated brush comes in direct contact with the work or substrate being coated, in this method there is no cost-effective means to restrict the coating from flowing down the sides of the three-dimensional object, or filling the voids between the three-dimensional object.
2) Spraying is a coating process whereby the fluent coating is dispensed through a nozzle under pressure resulting in a mist of the fluent coating being applied to the work or substrate, as in brushing there is no cost-effective means to restrict the coating to just the tips of the three-dimensional profile.
3) Slot Die/Curtain Coating, is a coating process comprised of a fixture containing the fluent coating and is typically positioned above the web, the bottom of the fixture containing the fluent coating contains an opening that can be controlled to regulate the volume of fluent coating being dispensed, this process is designed to deliver a uniform coating to the work or substrate and is not capable of restricting the application of the fluent to just the tip of the three-dimensional profile. The result is an overall coating and an undesirable volume of fluent deposition between the three-dimensional elements.
4) Direct gravure, is a coating process that relies on an engraved roller with a particular pattern of a particular geometric size, depth, shape and distance apart to retain the fluent coating for the purposes of transferring that coating directly onto the work or substrate surface. The engraved cells are specifically engineered to take into consideration the viscosity of the fluent coating and the resulting desired coat weight required to be applied to the surface of the work or substrate. In this process the fluent coating is metered into the cells of the “anilox roll” (engraved roller), most commonly by sitting in a bath of the fluent coating or the fluent coating is delivered to the anilox roll via an enclosed doctor blade system, in both cases a flexible metering blade comes into contact with the anilox surface, and is used to wipe the surface of the roll clean while maintaining the fluent coating in the engraved cells.
5) Reverse Gravure, is a coating process that utilizes similar coating apparatus as Direct Gravure (described in greater detail in, 4 above) whereby the application roll runs in the reverse direction of the work or substrate and requires kiss contact of the work or substrate being coated and is specifically designed to smear the fluent coating onto said work or substrate being coated. As in direct gravure, the fluent coating is metered via an anilox roll in conjunction with a flexible metering blade used to wipe the surface of the anilox roll clean while maintaining the fluent coating in the engraved cells.
6) Reverse roll, is a coating process typically comprised of 3 rolls in which the application roll is partially submerged into a slurry of fluent coating and said fluent coating is metered onto the application roll through a predetermined gap created between the application roll and the metering roll and said metering roll rotates in the reverse direction of the application roll, resulting in a uniform wet film thickness on the application roll, and whereby the application roll runs in the reverse direction of the web in order to transfer the fluent coating onto the work or substrate. The reverse direction of the application roll is designed to smear the fluent coating onto the work or substrate to minimize or eliminate coating defects caused by machine tolerance errors and or air bubbles in the fluent coating.
International Patent Application Publication No. WO 1997/007899 A1 to Iafrate discloses a “reverse gravure kiss coating system with output roller”, included in said application are drawings depicting multiple configurations of gravure coating processes including; direct gravure, differential speed gravure, reverse gravure, gravure kiss coater, and offset gravure coating configurations, all of which rely on cells engraved into the anilox roll in conjunction with a flexible metering blade used to wipe the surface of the anilox roll clean while maintaining the fluent coating in the engraved cells.
U.S. Pat. No. 5,275,657 to Duffy discloses a direct gravure application resulting in a thin layer of adhesive fluent to the tips of a three-dimensional corrugated profile “a doctor blade 142 wipes peripheral surface 140 of gravure roll 138 clean, leaving the adhesive compound only in the pits on the surface of gravure roll 138”.
U.S. Pat. No. 4,806,183 to Williams discloses a “Method of and apparatus for controlling application of glue to defined areas” including a means to apply adhesive were said application roll contains cells and in claim 12 identifies a gravure roll as the application roll “doctor means doctors substantially all of the adhesive off of said application roll peripheries except for adhesive in said cells”.
U.S. Patent Application Publication No. 2002/0108563 A1 to Yoshida discloses a two roll reverse coating system designed to apply a fluent coating directly to the surface of the work or substrate in a web coating application where the direction of the work or substrate being coated is traveling in the opposite direction of the application roll.
Disclosed in an article published in 1998, by Cambridge University Press “An experimental investigation of meniscus roll coating” describes a process utilizing a complex fluent delivery system to study and better understand the flow dynamics of a fluent coating when metered between 2 precision ground stainless steel rollers utilizing precision bearings with a surface roughness value out 0.4 μm.
The apparatus described above requires intimate or near intimate contact “kiss contact” to transfer the fluent coating from the application roll to the work or substrate. In both reverse and direct gravure the volume of said fluent coating is determined by the size, shape, angle and land area between cells. In order to extract the fluent coating from the cells, pressure created by the back-up roll is required. When attempting to coat a three-dimensional object the pressure required to affectively extract the adhesive from the gravure cells results in the adhesive flowing off the surface onto the sides of, and between said three-dimensional elements, or on the floor between same.
In the case of a Reverse Roll system, the application roll rotates in the reverse direction of the web and requires a “zero or near zero gap” between the application roll and the back-up roll that supports the work or substrate being coated to effect the transfer of the fluent coating onto said work or substrate. In both the Reverse Roll and Reverse Gravure, the reverse direction of the application roll with respect to the web direction combined with the “zero or near zero gap” requirements of the process results in the deposition of the fluent coating to flow and reside primarily on the side walls or on the floor between said three-dimensional elements.
This invention is to apply adhesive to the protrusion tips on a sheet of elastomeric material (cushion) that serves as a shock absorber and cushion for use between a flexographic printing plate and a printing cylinder during printing for compensating for variations in thickness, height and centricity of the printing cylinder and flexographic printing plate to prevent distortions in the image being printed that includes providing an elastomeric sheet having a longitudinal direction in the direction of circumferential travel of the cylinder circumference that includes a plurality or array of protrusions formed of the elastomeric material of predetermined cross-sectional shape and area and the material having a durometer to cushion the flexographic plate in such a way to provide the necessary compensation to ensure a high quality printed image at high speed.